WASHINGTON — Just two weeks after pleading guilty in a major federal fraud case, Amgen, the world's largest biotechnology firm, scored a largely unnoticed coup on Capitol Hill: Lawmakers inserted a paragraph into the "fiscal cliff" bill that strongly favored one of its drugs.

The language buried in Section 632 of the law delays a set of Medicare price restraints on a class of drugs that includes Sensipar, a lucrative Amgen pill used by kidney dialysis patients.

The provision gives Amgen an additional two years to sell Sensipar without government controls. The news was so welcome that the company's chief executive quickly relayed it to investment analysts. But it is projected to cost Medicare, and thus taxpayers, up to $500 million over that period.

Supporters of the delay, primarily leaders of the Senate Finance Committee who have long benefited from Amgen's political largess, said it was necessary to allow federal regulators to properly prepare for the pricing change. But critics, including several congressional aides, pointed out that Amgen had already won a previous two-year delay, and they depicted a second one as an unnecessary giveaway.

"That is why we are in the trouble we are in," said Dennis J. Cotter, a health policy researcher. "Everybody is carving out their own turf and getting it protected, and we pass the bill on to the taxpayer." The provision's inclusion in the legislation to avert the tax increases and spending cuts that made up the so-called fiscal cliff shows the enduring power of special interests in Washington.

Amgen has deep financial and political ties to lawmakers like Senate Minority Leader Mitch McConnell, R-Ky., and Sens. Max Baucus, D-Mont., and Orrin Hatch, R-Utah, who hold heavy sway over Medicare payment policy as the leaders of the Finance Committee.

It also has worked hard to build close ties with the Obama administration, with its lobbyists showing up more than a dozen times since 2009 on logs of visits to the White House.

Aides to Hatch and Baucus, and an Amgen spokesman, said the delay would give the Medicare system and medical providers time accommodate other complicated changes in how federal reimbursements for kidney care are determined.